1. Field
The present invention relates generally to systems and methods for rendering large images, such as maps, in client-server systems, and in one particular example, to client-side rendering of a map image according to received tiled vector image data.
2. Related Art
Various map and geographic information systems are known in the art. For example, various Web-based mapping services operating to deliver map image data to clients via a Web browser are known. Generally, the map image data may span large geographic areas and may be displayed in several discrete zoom levels. The map image data may further include various additional services, such as street names, addresses, and businesses for display with or overlaying the map image.
In a typical client-server environment, such as a Web based mapping service, map images are generally rendered on the server side in response to a user request for a map image and transferred to the client for display. For example, in response to a user request for a map image, a map server renders the appropriate image data for the location and zoom level associated with the request, renders the image data, and communicates the image data to the client (e.g., as JPEG or bitmap data). The image data is generally communicated to the client as raster image data, e.g., data for displaying an image as a collection of independently controlled dots or pixels arranged in rows and columns, which together form an image of the desired map. Raster image data may include bitmap data for producing the desired image, the bitmap data including a collection of pixels that represent an aerial or satellite photograph, graphical image, or the like of a geographical location (e.g., a city or neighborhood).
Map servers generally store terabytes or more of data associated with large map images and for transfer to clients (in some examples, however, the map data is not stored physically with the map server; rather, the map data is accessed by the map server from a local or remote database). The loading or rendering of map data for delivery to a client in response to a request is generally computationally burdensome on the server side, the client-side, or both. Accordingly, current Web based map image systems, e.g., based on rastor image data, generally suffer from several drawbacks. For example, zooming (or scaling) of the map image generally requires additional map data to be retrieved by the map server for display, and as such, generally requires greater storage and computational demands on the server to store and render each offered zoom level. Accordingly, as a client changes the zoom or pans within the map, there is often a time lag in the display of the map as the map server accesses, renders, and transfers the new map data corresponding to the new zoom level or view to the client.
Further, rastor images are generally optimized for display on a client display device such as a computer monitor or handheld device screen (e.g., at a resolution of approximately 1280×1024 and about 80-100 pixels per inch); however, such resolution optimized for display on a monitor is generally well below a desired resolution for printing. For example, typical printer resolution may be on the order of 600 dots per inch or greater such that printing a map rendered at a relatively low resolution (e.g., 80-100 pixels per inch) used for display results in relatively low quality printed image (compared with the printer's capability). Increased image resolution described for printing, however, would further burden the server, client, or both during map image rendering operations.
Accordingly, it is desired to provide a system and method for rendering images such as map images in a fast and efficient manner; for example, with reduced computational and storage demand on the server. Additionally, it is desirable to provide a system and method for rendering images that may be zoomed more efficiently and printed at higher resolution by a client.